Field of the Invention
The invention relates to magnetic recording heads, and more particularly, to a thin film magnetic core and coil apparatus and method of fabrication.
Description of Related Art
Miniaturization of magnetic recording devices and media has proceeded apace with the brisk diminution of computing devices and electronic circuits in general. A technological problem which has arisen with respect to the downsizing of magnetic recording devices concerns the reduced size of a magnetic recording head. As the size of magnetic recording heads has been reduced, the reading and writing sensitivity has decreased. Furthermore, a reduced size has made fabrication of the recording heads difficult. A magnetic recording head includes a infinitesimal magnetic coil which is wound around a tiny magnetic core. Typically, the magnetic coil is wound around the core by hand in an exceedingly delicate and time consuming operation.
Recently, a thin-film semiconductor fabrication technique has been used to construct magnetic coils for miniature magnetic recording heads. For example, A. Takayama et at. in U.S. Pat. No. 5,260,845, entitled "Magnetic Head Having a Thin Film Conductor Coil Assembly Formed Separate From a Magnetic Head Core", issued on Nov. 9, 1993, discusses a process for fabricating a thin film core. The fabrication process involves processing steps for forming seven layers, including a first insulating layer which is applied on a substrate, a lower coil layer, a second insulating layer, a magnetic core layer, a third insulating layer, an upper coil layer and a protective layer. The second insulating layer isolates the lower coil layer from the magnetic core layer. The third insulating layer isolates the upper coil layer from the magnetic core layer. The substrate is constructed from a ferrite block having grooves which are filled with glass. A dry etching process is used to construct the upper and lower coil layers and the magnetic coil layer, as well as for creating patterns in the insulating and protective layers. The magnetic coil and magnetic core layers are deposited by sputtering in argon gas, which is introduced into a sputtering chamber at a pressure typically between 2 milliTor and 20 milliTor, and are etched using a photoresist mask and ion beam milling. The magnetic coil layer is deposited by sputtering nickel-iron (81%-19%) permalloy to a thickness of 4 microns. The insulating layers are constructed of a thermosetted polyamide resin.
The performance of magnetic coils constructed using thin-film techniques is typically inferior to the performance of heads fabricated manually. Furthermore, the ferrite substrate is limited by present technological considerations to a 2.times.2 inch square block which is not a standard shape or material for semiconductor processing. The 2.times.2 inch square yields approximately 2500 units. Both the ferrite and glass materials in the composite substrate are inherently hard, noncompliant materials. Consequently, the surface at which the ferrite-glass substrate contacts overlying layers must be ground perfectly flat otherwise a gap may form between the magnetic materials, increasing the reluctance of the magnetic path and reducing the efficiency of the magnetic recording head.